Clutching a photo of her son, Maria Carvajal walks Tijuana's sweltering streets searching for the mentally disabled man she says was deported more than a month ago despite being a U.S. citizen and then disappeared in this chaotic border city.

Carvajal says she has searched hospitals, shelters and jails here looking for her 29-year-old son, Pedro Guzman of Lancaster, California, who was jailed for a misdemeanor trespassing violation, then sent to Mexico on May 11.

Guzman's relatives sued the Department of Homeland Security and the Los Angeles County Sheriff's Department last week in federal court, claiming Guzman was a U.S. citizen and had been wrongfully deported and demanding that U.S. authorities help find him.

"I'm searching for him because he's my son. But it should be (U.S. authorities) searching for him," Carvajal, a 49-year-old fast-food restaurant worker from Lancaster, said Sunday in Tijuana. "They made the mistake. Not me."

U.S. Immigration and Customs Enforcement confirmed Guzman had been deported and said the agency had done so correctly. "ICE has no reason to believe that it improperly removed Pedro Guzman," read a statement.

Officials at the U.S. consulate in Tijuana say they have made calls to help search for Guzman and asked other consulates in Mexico if they have information.

"We are doing things to help that we are not obliged to do," said consulate spokeswoman Lorena Blanco.

Carvajal, a brown-haired woman with glasses who carries a piece of paper bearing a photo of her son, said he called the family on May 11 to say he was deported but the phone cut off before she could find out where he was.

She said she never thought she would end up having to search Tijuana's hospital and morgues for her son, but vowed to keep on doing it because "I have to." She is not carrying her son's birth certificate with her, saying her main concern is finding him.

Guzman can't read or write and has trouble processing information. Carvajal fears he could be an easy victim for robbers.

The lawsuit says Guzman was asked about his immigration status in jail and responded that he was born in California of Mexican parents.

Sometime after that, the Sheriff's Department identified him as a non-citizen, obtained his signature for voluntary removal from the United States and turned him over to Customs and Immigration Enforcement, a division of the Homeland Security Department, for deportation.

The American Civil Liberties Union of Southern California, which helped file the lawsuit, says it has Guzman's birth certificate showing he was born at Los Angeles County-USC Medical Center.

It also says that Guzman had previously done jail time for drug possession, so he had a record that could have been cross-checked before a deportation decision was made.

The Sheriff's Department has said it followed procedures correctly.

In California, Guzman's brother, Michael Guzman, said last week that during a phone call to the family the 29-year-old said he had been deported and asked a passer-by where he was. The family could hear the person respond: "Tijuana."

Michael Guzman said his parents were from Mexico, but seven children, including Pedro, were born in California. Pedro, who takes the surname of his father, speaks both English and Spanish.

Carvajal said she keeps seeing glimpses of people on the Tijuana streets that she thinks are her son and runs toward them. But each time she finds she is mistaken.

"I have to fight for my son," she said.